/*
 * Copyright (C) 2011-2012 Free Software Foundation, Inc.
 *
 * Author: Nikos Mavrogiannopoulos
 *
 * This file is part of GnuTLS.
 *
 * The GnuTLS is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 3 of
 * the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>
 *
 */

/*
 * The following code is an implementation of the AES-128-GCM cipher
 * using intel's AES instruction set.
 */

#include <gnutls_errors.h>
#include <gnutls_int.h>
#include <gnutls/crypto.h>
#include <gnutls_errors.h>
#include <aes-x86.h>
#include <x86.h>
#include <byteswap.h>

#define GCM_BLOCK_SIZE 16

/* GCM mode */

typedef struct
{
  uint64_t hi, lo;
} u128;

/* This is the gcm128 structure used in openssl. It
 * is compatible with the included assembly code.
 */
struct gcm128_context
{
  union
  {
    uint64_t u[2];
    uint32_t d[4];
    uint8_t c[16];
  } Yi, EKi, EK0, len, Xi, H;
  u128 Htable[16];
};

struct aes_gcm_ctx
{
  AES_KEY expanded_key;
  struct gcm128_context gcm;
};

void gcm_init_clmul (u128 Htable[16], const u64 Xi[2]);
void gcm_ghash_clmul (uint64_t Xi[2], const u128 Htable[16],
                      const uint8_t * inp, size_t len);
void gcm_gmult_clmul (u64 Xi[2], const u128 Htable[16]);

static void
aes_gcm_deinit (void *_ctx)
{
  gnutls_free (_ctx);
}

static int
aes_gcm_cipher_init (gnutls_cipher_algorithm_t algorithm, void **_ctx, int enc)
{
  /* we use key size to distinguish */
  if (algorithm != GNUTLS_CIPHER_AES_128_GCM &&
      algorithm != GNUTLS_CIPHER_AES_256_GCM)
    return GNUTLS_E_INVALID_REQUEST;

  *_ctx = gnutls_calloc (1, sizeof (struct aes_gcm_ctx));
  if (*_ctx == NULL)
    {
      gnutls_assert ();
      return GNUTLS_E_MEMORY_ERROR;
    }

  return 0;
}

static int
aes_gcm_cipher_setkey (void *_ctx, const void *userkey, size_t keysize)
{
  struct aes_gcm_ctx *ctx = _ctx;
  int ret;

  ret = aesni_set_encrypt_key (userkey, keysize * 8, ALIGN16(&ctx->expanded_key));
  if (ret != 0)
    return gnutls_assert_val (GNUTLS_E_ENCRYPTION_FAILED);

  aesni_ecb_encrypt (ctx->gcm.H.c, ctx->gcm.H.c,
                     GCM_BLOCK_SIZE, ALIGN16(&ctx->expanded_key), 1);

  ctx->gcm.H.u[0] = bswap_64 (ctx->gcm.H.u[0]);
  ctx->gcm.H.u[1] = bswap_64 (ctx->gcm.H.u[1]);

  gcm_init_clmul (ctx->gcm.Htable, ctx->gcm.H.u);

  return 0;
}

static int
aes_gcm_setiv (void *_ctx, const void *iv, size_t iv_size)
{
  struct aes_gcm_ctx *ctx = _ctx;

  if (iv_size != GCM_BLOCK_SIZE - 4)
    return GNUTLS_E_INVALID_REQUEST;

  memset (ctx->gcm.Xi.c, 0, sizeof (ctx->gcm.Xi.c));
  memset (ctx->gcm.len.c, 0, sizeof (ctx->gcm.len.c));

  memcpy (ctx->gcm.Yi.c, iv, GCM_BLOCK_SIZE - 4);
  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 4] = 0;
  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 3] = 0;
  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 2] = 0;
  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 1] = 1;

  aesni_ecb_encrypt (ctx->gcm.Yi.c, ctx->gcm.EK0.c,
                     GCM_BLOCK_SIZE, ALIGN16(&ctx->expanded_key), 1);
  ctx->gcm.Yi.c[GCM_BLOCK_SIZE - 1] = 2;
  return 0;
}

static void
gcm_ghash (struct aes_gcm_ctx *ctx, const uint8_t * src, size_t src_size)
{
  size_t rest = src_size % GCM_BLOCK_SIZE;
  size_t aligned_size = src_size - rest;

  if (aligned_size > 0)
    gcm_ghash_clmul (ctx->gcm.Xi.u, ctx->gcm.Htable, src, aligned_size);

  if (rest > 0)
    {
      memxor (ctx->gcm.Xi.c, src + aligned_size, rest);
      gcm_gmult_clmul (ctx->gcm.Xi.u, ctx->gcm.Htable);
    }
}

static inline void
ctr_encrypt_last (struct aes_gcm_ctx *ctx, const uint8_t * src,
                  uint8_t * dst, size_t pos, size_t length)
{
  uint8_t tmp[GCM_BLOCK_SIZE];
  uint8_t out[GCM_BLOCK_SIZE];

  memcpy (tmp, &src[pos], length);
  aesni_ctr32_encrypt_blocks (tmp, out, 1, ALIGN16(&ctx->expanded_key), ctx->gcm.Yi.c);

  memcpy (&dst[pos], out, length);

}

static int
aes_gcm_encrypt (void *_ctx, const void *src, size_t src_size,
                 void *dst, size_t length)
{
  struct aes_gcm_ctx *ctx = _ctx;
  int blocks = src_size / GCM_BLOCK_SIZE;
  int exp_blocks = blocks * GCM_BLOCK_SIZE;
  int rest = src_size - (exp_blocks);
  uint32_t counter;

  if (blocks > 0)
    {
      aesni_ctr32_encrypt_blocks (src, dst,
                                  blocks, ALIGN16(&ctx->expanded_key), 
                                  ctx->gcm.Yi.c);

      counter = _gnutls_read_uint32 (ctx->gcm.Yi.c + 12);
      counter += blocks;
      _gnutls_write_uint32 (counter, ctx->gcm.Yi.c + 12);
    }

  if (rest > 0)                 /* last incomplete block */
    ctr_encrypt_last (ctx, src, dst, exp_blocks, rest);

  gcm_ghash (ctx, dst, src_size);
  ctx->gcm.len.u[1] += src_size;

  return 0;
}

static int
aes_gcm_decrypt (void *_ctx, const void *src, size_t src_size,
                 void *dst, size_t dst_size)
{
  struct aes_gcm_ctx *ctx = _ctx;
  int blocks = src_size / GCM_BLOCK_SIZE;
  int exp_blocks = blocks * GCM_BLOCK_SIZE;
  int rest = src_size - (exp_blocks);
  uint32_t counter;

  gcm_ghash (ctx, src, src_size);
  ctx->gcm.len.u[1] += src_size;

  if (blocks > 0)
    {
      aesni_ctr32_encrypt_blocks (src, dst,
                                  blocks, ALIGN16(&ctx->expanded_key), 
                                  ctx->gcm.Yi.c);

      counter = _gnutls_read_uint32 (ctx->gcm.Yi.c + 12);
      counter += blocks;
      _gnutls_write_uint32 (counter, ctx->gcm.Yi.c + 12);
    }

  if (rest > 0)                 /* last incomplete block */
    ctr_encrypt_last (ctx, src, dst, exp_blocks, rest);

  return 0;
}

static int
aes_gcm_auth (void *_ctx, const void *src, size_t src_size)
{
  struct aes_gcm_ctx *ctx = _ctx;

  gcm_ghash (ctx, src, src_size);
  ctx->gcm.len.u[0] += src_size;

  return 0;
}


static void
aes_gcm_tag (void *_ctx, void *tag, size_t tagsize)
{
  struct aes_gcm_ctx *ctx = _ctx;
  uint8_t buffer[GCM_BLOCK_SIZE];
  uint64_t alen, clen;

  alen = ctx->gcm.len.u[0] * 8;
  clen = ctx->gcm.len.u[1] * 8;

  _gnutls_write_uint64 (alen, buffer);
  _gnutls_write_uint64 (clen, &buffer[8]);

  gcm_ghash_clmul (ctx->gcm.Xi.u, ctx->gcm.Htable, buffer, GCM_BLOCK_SIZE);

  ctx->gcm.Xi.u[0] ^= ctx->gcm.EK0.u[0];
  ctx->gcm.Xi.u[1] ^= ctx->gcm.EK0.u[1];

  memcpy (tag, ctx->gcm.Xi.c, MIN (GCM_BLOCK_SIZE, tagsize));
}

const gnutls_crypto_cipher_st aes_gcm_struct = {
  .init = aes_gcm_cipher_init,
  .setkey = aes_gcm_cipher_setkey,
  .setiv = aes_gcm_setiv,
  .encrypt = aes_gcm_encrypt,
  .decrypt = aes_gcm_decrypt,
  .deinit = aes_gcm_deinit,
  .tag = aes_gcm_tag,
  .auth = aes_gcm_auth,
};
